This is a comparative double blind, double dummy, randomized study on the effectiveness of Diclofenac potassium versus Acetaminophen in febrile children with acute upper respiratory tract infections. The patient will be randomized to either group: Group A (Diclofenac potassium (0.5 mg/kg) or Group B (Acetaminophen (10 mg/kg)). A Health Care Professional trained will measure the temperature during 2 hours. During the study period, parents or legal representatives will be invited to fill a survey about the habits and knowledge regarding fever management at home.